Total lunar eclipse, 16 May 2022

A guide to the total lunar eclipse of 16 May 2022

Published: May 13, 2022 at 10:44 am
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A total eclipse of the Moon was visible in the early hours of this Monday 16 May 2022, beginning at 03:27 BST from the UK, with totality occurring at 04:29 BST.

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The Moon was low above the southwest horizon as the initial partial stage of the eclipse began and remained in this general direction as totality was reached at 04:29 BST.

The Moon set at 05:10 BST.

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Eric Robinson captured this pic of the 16 May lunar eclipse from Albuquerque, New Mexico, USA with his iPhone 12. Equipment: iPhone 12, 14-inch Sky-Watcher 350P flex tube Dobsonian, 32mm eyepiece
Eric Robinson captured this pic of the 16 May lunar eclipse from Albuquerque, New Mexico, USA with his iPhone 12. Equipment: iPhone 12, 14-inch Sky-Watcher 350P flex tube Dobsonian, 32mm eyepiece

What is a total lunar eclipse and when do they happen?

Mechanics of a lunar eclipse. Credit: NASA

Lunar eclipses don't happen more regularly because the Moon’s 5˚ orbital tilt normally has it passing above or below Earth’s shadow in space.

It’s only when there’s a straight-line alignment between the Sun, Earth and Moon that the Moon crosses into Earth’s shadow.

When this happens, the observers on Earth’s hemisphere facing the Moon witness a lunar eclipse.

This is what will happen on the morning of 16 May 2022, when we in the UK will be in the right hemisphere for the first half of the eclipse.

Understanding the penumbra and umbra

The cone-shaped shadow of the Moon cast by the Sun creates an umbra and penumbra on Earth. Credit: Science Photo Library
The cone-shaped shadow of the Moon cast by the Sun creates an umbra and penumbra on Earth. Credit: Science Photo Library

At the Moon’s distance, Earth’s shadow has two parts: a weak outer penumbra and a dark umbra.

The penumbral shadow is the region where, if you were on the Moon looking back towards the Sun, you would see it partially eclipsed by Earth.

At the outer edge of this shadow the partial solar eclipse would be tiny, increasing in magnitude the deeper into the penumbra you go.

The umbral shadow sits at the centre of the penumbra and is the part of Earth’s shadow where all of the Sun’s light would be blocked from view.

The darkness of the penumbra increases towards the umbra.

Why is a lunar eclipse red?

Lunar Eclipse (28/09/2015) by Susan Snow, Bishops Cleeve, Cheltenham, UK.
Lunar eclipse on 28 September 2015 by Susan Snow, Bishops Cleeve, Cheltenham, UK. Equipment: Canon EOS 600D with a 300mm lens.

Earth casts an interesting shadow because it has an atmosphere.

Light skimming the edge of our planet is refracted to partly infill the umbra.

As our atmosphere scatters blue light, light that has passed through it tends towards the redder end of the spectrum, giving the umbra a red or orange colour.

How to see the 16 May total lunar eclipse

A chart showing the phases of the total lunar eclipse from the UK on 16 May 2022. Credit: Pete Lawrence
Credit: Pete Lawrence

The total lunar eclipse of 16 May kicks off with the penumbral eclipse at 02:32 BST (01:32 UT).

This is a weak part of any lunar eclipse and difficult to detect.

As the Moon moves deeper into the penumbra the shadow’s depth increases, and you’re likely to see this as a dark shading near the western limb.

It becomes darker until the Moon encounters the umbral shadow at 03:27 BST (02:27 UT).

Lunar Eclipse (28/09/2015) by Sarah & Simon Fisher, Bromsgrove, Worcestershire, UK.
The phases of a lunar eclipse by Sarah & Simon Fisher, Bromsgrove, Worcestershire, UK. Equipment: Canon 600D attached to Maksutov 127mm telescope, Prime Focus single shots

The umbral shadow is distinct and darker than the penumbra. The ensuing partial phase of the eclipse grows in magnitude until, at 04:29 BST (03:29 UT), the Moon is engulfed in dark shadow: this is the start of totality.

All the while, dawn will be progressing to create an interesting conundrum.

Whereas a bright non-eclipsed Moon is easy to see against bright sky, an eclipsed Moon against such a sky may seem to vanish from view, depending on the eclipse’s darkness.

From the UK, the Moon sets just after the point of greatest eclipse, timed for 05:11 BST (04:11 UT).

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This guide originally appeared in the May 2022 issue of BBC Sky at Night Magazine.

Authors

Pete Lawrence, astronomer and BBC The Sky at Night presenter.
Pete LawrenceAstronomer and presenter

Pete Lawrence is an experienced astronomer and astrophotographer, and a presenter on BBC's The Sky at Night.

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